Why does Atheism=no religion?

I will admit I was a Christian at one point, but just as Christians and Catholics say their religion is the way to life, us atheists look at their lifestyle as a way to our lives. I don't say I disagree with it to be a huge d*ck, I say it because it's my beliefs. I'm an open minded and calm person, please don't say "all atheists blah blah blah" because it's pretty offending.